While methods of coupling reinforcing bar (rebar) are well known in the building industry, solutions to problems associated with accurately positioning pre-cast concrete structures prior to joining rebar, have not to date, enjoyed similar progress. In almost all situations, the prior art solution is commonly dependent on first locating and independently supporting the concrete structures with respect to each other by cranes or props. This then is followed by the connection of associated reinforcement bars or rods protruding from the respective concrete structures. Invariably, the bars are often not perfectly aligned as a result of when the bars were initially cast in the concrete structures themselves.
Prior art rebar connection means are as varied as the building construction. A common method of connecting the bars is by overlapping and tie wiring them together with a stipulated overlap length of normally thirty to forty times individual bar diameter. While this method does not require overlapping bars to be accurately and co axially aligned, a plurality of them can create congestion within the confines of the limited construction space. This invariably results in the concrete elements having to be larger simply to accommodate the greater space occupied by the number of overlapping and wire tied bars. While this method is common practice for in-situ cast structures, it becomes even more complicated when the opposing structural elements are precast away from the building, for example, at a remote factory location. In that case, at least one concrete element would need to have voids cast into it to accommodate the extra space required by the overlapping procedure. The voids also need to be big enough to allow for any misalignment of the bars which are then grout or epoxy filled in order to permanently intergrate the connection. The concrete elements need to be propped or braced until the supporting concrete structure cures and must be safely secured during the entire building procedure. As a consequence, there is an unavoidable degree of complexity and material wastage associated with this method which is not only expensive but is also time and labour intensive. Another method of joining reinforcement bars utilises mechanical device connectors which are threaded or attached by an epoxy adhesive adapted to join the ends of the rebar. The use of mechanical connectors however invariably requires the bars to be very closely or near perfectly aligned. Moreover, this method is usually satisfactory if there is only a single bar to be joined to an opposite bar. Australian Patent 2003210074 and WO98/44215 (Barfix Bermuda Ltd) describe a method and device for joining steel bars involving a connecting element with a thread cutter to cut a conical screw at one end of a reinforcement bar.
AU2001051968 discloses a structural bracing system involving a lockable nut used with a threaded steel bar which includes a locking member engaged with the bar. The locking member has a finger to engage the locking nut with the end of the finger being displaced as a result of the deformation of a finger actuated tab.
In all of the above prior art, the methods and apparatus for connecting reinforcing bars are reliant on their perfect or near perfect alignment with their opposite numbers. In most situations, there are often multiple bars which are required to be connected as a group. Needless to say, it is a highly skilled and labour intensive task to ensure that all bars of one group are accurately aligned with the corresponding bars of an opposite group.
Significantly, nothing in the preceding examples however provides for the ability to selectively lift or push apart strategically selected opposing bars to adjust the positions of the associated concrete structures. While previously mentioned, in almost all situations where stacked or vertically aligned concrete structures are involved, the solution is commonly to locate and support the structures temporarily with props or other means prior to actually joining them together. This procedure is complicated and multi-stepped and often results in reinforcement bars becoming no longer aligned and ultimately too difficult to successfully connect.
A recent solution to this problem has been the development of a combination coupler and column alignment device disclosed in WO 2014/000038. This coupler utilises an adjustment nut screwed on a threaded rebar stud. In use, the adjustment nut is forcibly jacked against washers functioning as bearing surfaces of a coupler member screwed on an opposing rebar stud. An important consideration with this coupler, as with all the previous examples, is the need to align or centre the rebar prior to actually joining them together. Like the other prior art couplers, this coupler relies on generous internal diameters to accommodate misalignment of the rebar. Furthermore, this coupler utilises multiple threaded and non-threaded components to affect the transfer of forces to the rebar. The problem with the addition of each separate component, is that the total risk of potential failure is correspondingly also increased. When the coupler is safety tested, the total inherent slippage or elongation dramatically rises with each threaded component. This can result in the devices ultimately failing or not meeting the relevant engineering and safety standards. Although one solution is to increase the size of various components (in the attempt to reduce the total slippage or elongation), large couplers can make them difficult or impossible to use in the limited spaces normally afforded between the concrete elements to be joined. In addition, larger sized couplers not only use more steel but can require more time and labour to manufacture and/or assemble.
It is thus a general object of the present invention to ameliorate or eliminate some if not all of the problems and disadvantages associated with the prior art. In the least, it seeks to provide the public with an alternative commercially useful choice. As the invention is specifically directed to the removal of external supports normally used to position concrete structures during construction, the principle object is thus to provide a compact, self-centring and lifting coupler with a substantially reduced number of parts (e.g. adjustment nuts) and bearing surfaces (e.g. washers), thereby reducing total inherent slippage or elongation to comply with the most demanding of industrial safety standards.